An easy to use, low-cost system is needed for measuring and assessing gait kinematic parameters for purposes of screening for fall risk in clinical settings (e.g., physician's offices) and senior-care facilities, as well as for use by researchers. Such a system would also be valuable in various other applications where body segment 6-DOF three-dimensional (3-D) motion tracking is needed. Examples of such applications include outcome evaluation after total knee or hip replacement, external prosthesis adjustment for amputees, monitoring of rehabilitation progress, and gait analysis in patients with neurological diseases. Presently available systems for measuring gait parameters are limited by one or more of the following constraints: (1) small "capture volumes" that severely limit the number of contiguous steps that can be collected without interruption (e.g., turns); (2) collection of temporal gait information only (no spatial parameters); (3) high cost; and/or (4) inconvenience (e.g., need to mount foot switches within shoes or taped to the bottoms of the feet, access to a motion laboratory, etc.). Barren Associates, Inc. (BAI) and its subcontractor, the University of Kansas, propose to develop a wireless six degree-of-freedom (6-DOF) Ankle Inertial Measurement System (AIMS) that can collect and extract generic gait measures and process the gait parameter data to assess a subject's prospective fall risk. The proposed technology will simplify and expand access to accurate gait measurement technology, allowing it to be used in many more applications and on individuals in their natural environments.